Characterization of unconventional hydrogen flame propagation in narrow gaps

The physical limits of the unconventional flame propagation regimes recently discovered [Veiga-Lopez et al., Phys. Rev. Lett. 124, 174501 (2020)] are analyzed. These appear in combustible gaseous mixtures approaching lean quenching limit hydrogen-air flames narrow gaps. They characterized by a split front into dendritic and bifurcating set cells separated nonburned material. A feature selection analysis utilizing dimensionless numbers is applied to reveal most significant parameters governing separation between traditional regimes. It concluded that (a) outbreak mostly due heat losses, (b) phenomenon governed Peclet number only appears thin channels, (c) Lewis does not determine regime. Additionally, an equation describing optimal border regime derived from experiments.